A cab is a component of the passenger boarding bridge that comes into direct contact with a aircraft door when an aircraft is in a stop position. In order to achieve a close and reliable connection between the cab and the aircraft door, it is required to adjust a docking angle of the cab, and thereby the cab is pivotably connected to the tunnel and is driven by the rotationally driving device to rotate around a cabin of the tunnel.
The rotationally driving device of the existing cab is composed of a driving motor, a chain, sprocket wheels, wherein the driving motor is fixedly mounted on the cab, and drives the sprocket wheels to connect with an output shaft of the driving motor via an appropriate reducing mechanism. The chain is fixed on the tunnel, and in particular on the periphery of the cabin. The chain can be engaged with the driving sprocket wheel and engaged with an appropriate intermediate sprocket wheel. During operation, the driving motor is rotated such that the driving sprocket wheel is rotatable while engaging with the chain, thereby driving the cab to rotate around the cabin.
However, the existing rotationally driving device has a risk of chain disconnection, which becomes a major factor for lose effectiveness of the cab rotating system. As a result of this, it is required to improve the existing technology to improve safety factor of docking the cab with the aircraft door.
In order to solve the above problem and improve the safety margin, a double-chain driving device of the cab of the passenger boarding bridge was disclosed in Chinese Patent Application (No. CN10299169A) as filed on Oct. 16, 2012. The double-chain driving device includes a driving motor, a first sprocket wheel and a double-row chain. The driving motor drives the first sprocket wheel, and the first sprocket wheel can be engaged with the double-row chain to drive the cab rotatable relative to the tunnel. The minimum breaking force of the chain can be doubled by using a double-row chain. In addition, the chain also includes a detection device for detecting working state of the chain on the ends, to make an alarm when the chain is disconnected or a nut for fixing the chain is loosened. The above patent application is incorporated by reference as if set forth herein.
In the above solution, at least double-chain drives jointly to reduce the risk caused when one of the chains is broken. And, the detection device may make a fault alarm in time when the fault occurs.
However, there are still some detects in the existing solutions described above, for example, reaction for the chain being broken may be lagged, thereby the driving device in a normal operation cannot prompt that the chain is broken. Internal friction caused by different tightness of the two chains can be increased and an auxiliary chain is worn severely, thereby the follow-up maintenance cost will be increased. Despite provision of a detection device and an alarm device, no further measure taken for the chain disconnection can be provided, which cannot avoid occurrence of device damage, and even danger against the personnel's life.
The information as disclosed in the technical background portion merely serves to reinforce understanding of the background of the present disclosure, thereby including information that does not form the prior art that has been already known by the person skilled in the art.